Method and apparatus for adaptive impedance matching

ABSTRACT

A system that incorporates teachings of the present disclosure may include, for example, an adaptive impedance matching network having an RF matching network coupled to at least one RF input port and at least one RF output port and comprising one or more controllable variable reactive elements. The RF matching network can be adapted to reduce a level of reflected power transferred from said at least one input port by varying signals applied to said controllable variable reactive elements. The one or more controllable variable reactive elements can be coupled to a circuit adapted to map one or more control signals that are output from a controller to a signal range that is compatible with said one or more controllable variable reactive elements. Additional embodiments are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/217,748 filed Aug. 25, 2011, which was a continuation of U.S. patentapplication Ser. No. 12/722,156 filed Mar. 11, 2010 now U.S. Pat. No.8,217,732, which was a continuation of U.S. Pat. No. 7,714,676 filed onNov. 8, 2006, the disclosures of all of which are hereby incorporated byreference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to matching networks, and morespecifically to a method and apparatus for adaptive impedance matching.

BACKGROUND

A function of an adaptive impedance matching module can be to adaptivelymaximize the RF power transfer from its input port to an arbitrary loadimpedance that changes as a function of time.

A consideration of an impedance matching control system is the dynamicrange of input power over which it will operate. Low cost RF voltagedetectors such as a diode detector have been used, but with a limiteddynamic range. Logarithmic amplifiers (that detect a signal envelope)can have a higher dynamic range than diode detectors, but their cost,complexity, chip area, and current drain can be higher.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustrative embodiment of a block diagram of acontrol system;

FIG. 2 depicts an illustrative embodiment of a control system for amulti-port adaptive impedance matching module;

FIG. 3 depicts an illustrative embodiment of a closed loop controlsystem; and

FIGS. 4-6 depict illustrative embodiments of an adaptive impedancematching module with enhanced dynamic range.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the presentdisclosure. However, it will be understood by those skilled in the artthat the present disclosure may be practiced without these specificdetails. In other instances, well-known methods, procedures, componentsand circuits have not been described in detail so as not to obscure thepresent disclosure.

Some portions of the detailed description that follows are presented interms of algorithms and symbolic representations of operations on databits or binary digital signals within a computer memory. Thesealgorithmic descriptions and representations may be the techniques usedby those skilled in the data processing arts to convey the substance oftheir work to others skilled in the art.

An algorithm is here, and generally, considered to be a self-consistentsequence of acts or operations leading to a desired result. Theseinclude physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. It has proven convenient at times,principally for reasons of common usage, to refer to these signals asbits, values, elements, symbols, characters, terms, numbers or the like.It should be understood, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” or the like, can refer to the actionand/or processes of a computer or computing system, or similarelectronic computing device, that manipulate and/or transform datarepresented as physical, such as electronic, quantities within thecomputing system's registers and/or memories into other data similarlyrepresented as physical quantities within the computing system'smemories, registers or other such information storage, transmission ordisplay devices.

Embodiments of the present disclosure may include apparatuses forperforming the operations herein. An apparatus can be speciallyconstructed for the desired purposes, or it can comprise a generalpurpose computing device selectively activated or reconfigured by aprogram stored in the device. Such a program may be stored on a storagemedium, such as, but not limited to, any type of disk including floppydisks, optical disks, compact disc read only memories (CD-ROMs),magnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), electrically programmable read-only memories (EPROMs),electrically erasable and programmable read only memories (EEPROMs),magnetic or optical cards, or any other type of media suitable forstoring electronic instructions, and capable of being coupled to asystem bus for a computing device.

The processes and displays presented herein are not inherently relatedto any particular computing device or other apparatus. Various generalpurpose systems can be used with programs in accordance with theteachings herein, or it may prove convenient to construct a morespecialized apparatus to perform the desired method. The desiredstructure for a variety of these systems will appear from thedescription below. In addition, embodiments of the present disclosureare not described with reference to any particular programming language.It will be appreciated that a variety of programming languages may beused to implement the teachings of the present disclosure as describedherein. In addition, it should be understood that operations,capabilities, and features described herein may be implemented with anycombination of hardware (discrete or integrated circuits) and software.

Use of the terms “coupled” and “connected”, along with theirderivatives, can be used. It should be understood that these terms arenot intended as synonyms for each other. Rather, in particularembodiments, “connected” may be used to indicate that two or moreelements are in direct physical or electrical contact with each other.

“Coupled” can be used to indicated that two or more elements are ineither direct or indirect (with other intervening elements between them)physical or electrical contact with each other, and/or that the two ormore elements co-operate or interact with each other (e.g. as in a causean effect relationship).

One embodiment of the present disclosure can entail an apparatus havingan RF matching network coupled to at least one RF input port and atleast one RF output port and comprising one or more controllablevariable reactive elements. The RF matching network can be adapted toincrease RF power transferred from said at least one RF input port tosaid at least one RF output port by varying signals supplied to saidcontrollable variable reactive elements to increase the RF voltage atsaid at least one RF output port. The one or more controllable variablereactive elements can be coupled to a bias driver circuit adapted to mapone or more control signals that are output from a controller to asignal range that is compatible with said one or more controllablevariable reactive elements in said RF matching network.

One embodiment of the present disclosure can entail an adaptiveimpedance matching network having an RF matching network coupled to atleast one RF input port and at least one RF output port and comprisingone or more controllable variable reactive elements. The RF matchingnetwork can be adapted to reduce a level of reflected power transferredfrom said at least one input port by varying signals applied to saidcontrollable variable reactive elements. The one or more controllablevariable reactive elements can be coupled to a circuit adapted to mapone or more control signals that are output from a controller to asignal range that is compatible with said one or more controllablevariable reactive elements.

One embodiment of the present disclosure can entail a machine-readablestorage medium having computer instructions to vary control signals thatchange one or more reactances within an RF matching network to increasean RF output voltage at an RF output port of said RF matching network.The RF matching network can have one or more controllable variablereactive elements, which can be coupled to a circuit adapted to map thecontrol signals to a signal range that is compatible with said one ormore controllable variable reactive elements.

An embodiment of the present disclosure can provide closed-loop controlof an adaptive impedance matching module (AIMM) having RF input andoutput ports. The RF output node voltage of the AIMM tuner circuit canbe monitored and maximized to achieve a desirable impedance match to anarbitrary load impedance. In addition, improvement in dynamic range canbe achieved by adaptively changing the RF coupling level between thevoltage sensed at the output port (e.g., antenna side) of the matchingnetwork and the voltage provided to the detector. This coupling levelcan be controlled by a processor which can perform closed loop tuning. Asimple voltage divider comprised of resistors and a digitally controlledRF switch can be used to realize variable coupling levels, although thepresent disclosure is not limited in this respect. Another means ofrealizing variable coupling levels is to digitally switch betweendifferent tap points in a series string of variables capacitors whichform a shunt voltage tunable dielectric capacitor at the output node ofthe AIMM tuner.

A function of an adaptive impedance matching module (AIMM) can be toadaptively maximize the RF power transfer from its input port to anarbitrary load impedance ZL where the load can be variable. Turning nowto the figures, FIG. 1, shown generally as 100, is an embodiment AIMMblock diagram.

The RF matching network 110 can contain inductors and capacitors totransform an arbitrary load impedance Z_(L) 135 to an impedance equal toor close to a defined system impedance, such as 50 Ohms A benefit ofthis transformation is an improvement in a level of power transferred tothe load impedance Z_(L) 135, and a reduction in the level of reflectedpower from the RF input port 105. This second benefit can be referred toas an improvement in the input mismatch loss where mismatch loss isdefined as (1−|S₁₁|²).

The RF matching network 110 can contain one or more variable reactiveelements which can be voltage controlled. The variable reactive elementscan be, although are not required to be, variable capacitances, variableinductances, or both. In general, the variable capacitors can besemiconductor varactors, micro-electro-mechanical systems (MEMS)varactors, MEMS switched capacitors, ferroelectric capacitors, or anyother technology that implements a variable capacitance. The variableinductors can be switched inductors using various types of RF switchesincluding MEMS-based switches. The reactive elements can also be currentcontrolled rather than voltage controlled without departing from thespirit and scope of the present disclosure.

The variable capacitors of the RF matching network can be tunableintegrated circuits, such as voltage tunable dielectric capacitors orParascan Tunable Capacitors (PTCs). Each tunable capacitor can berealized as a series network of capacitors which are all tuned using acommon tuning voltage.

The RF voltage detector 130 of FIG. 1 can be used to monitor themagnitude of the output nodal voltage. A fundamental concept used inthis control system can be that the RF power transferred to thearbitrary load impedance 135 is maximized when the RF voltage magnitudeat the output port 115 is maximized. It is the understanding of thisconcept that allows one to remove a directional coupler conventionallylocated in series with the input port and to thus simplify thearchitecture of the control system.

A directional coupler can be undesirable for numerous reasons: (1) Thecost of the coupler can be undesirable. (2) The physical size of thedirectional coupler can be prohibitive. For example, broadband couplerscan be typically ¼ of a guide wavelength in total transmission linelength at their mid-band frequency. For a 900 MHz band and an effectivedielectric constant of 4, the total line length needs to be about 1.64inches. (3) The directivity of the directional coupler can set a lowerlimit on the achievable input return loss of the RF matching network.For instance, a directional coupler with 20 db of coupling can limit theinput return loss for the AIMM to about −20 dB. (4) Directional couplerscan have limited operational bandwidth, where the directivity meets acertain specification. In some applications, the AIMM can need to workat different frequency bands separated by an octave or more, such as at900 MHz and 1900 MHz in a commercial mobile phone.

The RF voltage detector 130 can be comprised of a diode detector, atemperature compensated diode detector, a logarithmic amplifier, or anyother means to detect an RF voltage magnitude. The phase of the RFvoltage is not required. The controller 125 can accept as an input theinformation associated with the detected RF output 115 voltage. Thecontroller 125 provides one or more outputs that control a bias voltagedriver circuit 120. The controller 125 can be digitally-based such as amicroprocessor, a digital signal processor, or an ASIC, or any otherdigital state machine. The controller can also be an analog-basedsystem.

The bias voltage driver circuit 120 can map control signals that areoutput from the controller 125 to a voltage range that is compatiblewith the tunable reactive elements in the RF matching network 110. Thedriver circuit 120 can be an application specific integrated circuit(ASIC) whose function is to accept digital signals from the controller125 and then output one or more analog voltages for one or more tunablereactive elements in the RF matching circuit 110. The driver circuit 120can provide a wider range of analog tuning voltages than what is used asa power supply voltage by the controller 125. Hence the driver circuit120 can perform the functions of voltage translation and voltagescaling.

A purpose of the control system shown in FIG. 1 can be to monitor theoutput RF voltage magnitude of the RF matching circuit 110 and to usethis information as an input to an algorithm that adjusts the tuningvoltages provided to the tunable reactive elements in the RF matchingnetwork 110. The algorithm can adjust the reactances to maximize the RFoutput 115 voltage. Various options exist for control algorithms. Ingeneral, the algorithm can be a scalar multi-dimensional maximizationalgorithm where the independent variables are the tuning voltages forthe reactive elements.

The simplified control system shown in FIG. 1 is illustrated using a 2port RF matching network. However, this control system is extensible tomulti-port RF matching networks as shown in FIG. 2, generally as 200.Consider an RF multiplexing filter with N input ports where each port isdesigned for a specific band of frequencies. Assume that N transmittersdrive the N input ports 205, 210, 215 and 220, and that each input portis coupled to the single RF output port 240 using RF circuits thatcontain variable reactive elements. The objective of the control systemremains the same, to maximize the RF output voltage magnitude, and thusto optimize the power transfer from the n^(th) input port to anarbitrary load impedance. Further, the RF voltage detector 245,controller 235 and bias voltage driver circuit 230 function as describedabove with reference to FIG. 1 and in the embodiment of FIG. 2, the RFmatching network is a multi-port RF matching network 225.

Although the present disclosure is not limited in this respect, thearbitrary load impedance Z_(L) 250 can be a multi-band antenna in amobile wireless device and the multi-port matching network 225 can be adiplexer whose function is to route the signal between two or more pathsby virtue of its signal frequency.

Looking now at FIG. 3, the variable capacitors (such as, but not limitedto, PTCs) 320, 325 and 330 and inductors 305 and 310 can be built into amultichip module 300 containing a detector 360, an analog-to-digitalconverter (ADC) 365, a processor 355, digital-to-analog converters(DACs) 370, voltage buffers, and a charge pump 335. This multichipmodule 300 can be designed with a closed loop feedback system tomaximize the RF voltage across the output node by adjusting all the PTC320, 325 and 330 bias voltages, and doing so independently.

In an embodiment of the present disclosure as provided in FIG. 3, the RFmatching network can be comprised of inductors L₁ 310, L₂ 305 andvariable capacitors PTC₁ 320, PTC₂ 325 and PTC₃ 330. Note that eachvariable capacitor can itself be a complex network. The RF voltagedetector 360 in this AIMM can be comprised of a resistive voltagedivider (5 KΩ/50Ω) and the simple diode detector. In an embodiment ofthe present disclosure, the controller can be comprised of ADC₁ 355, themicroprocessor 355, plus the DAC₁ 370, DAC₂ 375 and DAC₃ 380. Thecontroller can use external signals such as knowledge of frequency, Txor Rx mode, or other available signals in the operation of its controlalgorithm. The bias voltage driver circuit can be comprised of aDC-to-DC converter such as the charge pump 335, in addition to the threeanalog buffers whose output voltage is labeled V_(bias1) 385, V_(bias2)390, and V_(bias3) 395. The DC-to-DC voltage converter can be used tosupply a higher bias voltage from the analog buffers than what isnormally required to power the processor 355. The charge pump can supplya voltage in the range of 10 volts to 50 volts, and in some embodiments,both positive and negative supply voltages can be used.

It should be noted that the RF matching network shown in FIG. 2 isrepresentative of many possible circuit topologies. Shown in FIG. 2 is aladder network, but other topologies such as a T or Pi network can beused. The variable reactive elements (capacitors) are shown in shuntconnections but that is not a restriction, as they can be used in seriesin other applications. Furthermore, three independent variablecapacitances are shown in this RF matching network. However, fewer ormore variable reactive elements can be used depending on the complexityneeded to meet RF specifications.

In FIG. 3, the inductors for the RF matching network are shown to beincluded in the AIMM multichip module. In practice, this may not alwaysbe the case. If the module is extremely small, it can be more convenientto use external inductors for the matching network. External inductorscan have a higher Q factor than smaller inductors that are able to beintegrated on the module.

An embodiment of the AIMM control system is the dynamic range of inputpower over which it can operate. A low cost RF voltage detector can be asimple diode detector, but it can have a limited dynamic range of about25 dB. Logarithmic amplifiers (that detect the signal envelope) can havea much higher dynamic range of 50 dB to 60 dB, but their cost,complexity, chip area, and current drain is also much higher.

In an embodiment of the present disclosure, as illustrated in FIG. 4 at400, one can use a variable voltage divider to improve the dynamic rangeof a simple diode detector. The variable voltage divider 430 can beadded between the RF output port 435 and the RF voltage detector 425. Itcan be controlled by the loop controller 420 (microprocessor, ASIC,etc), and therefore it is a programmable voltage divider. Bias voltagedriver circuit 415 and RF matching network 410 can operate as describedabove with respect to FIG. 1.

As shown in FIG. 5, an embodiment of the present disclosure provides asimple resistive voltage divider 550 which can be implemented using athree-pole RF switch 560 to select one of three different resistances:R1 530, R2 535, or R3 540. Although not limited in this respect, typicalvalues can be 100Ω, 1K Ω, and 10 K Ω. A typical value for R4 565 can be50Ω, which can be a desirable value for most RF detector designs.Assuming a high input impedance for the detector 555, the voltagecoupling levels can be ⅓, 1/21, and 1/201.

This corresponds to voltage coupling levels of −9.5 dB, −26.4 dB, and−46 dB. At high power levels the lowest coupling can be desirable. Atlow power levels, the highest coupling level can be desirable. A dynamicrange of the control loop can equal to that of the detector plus thedifference in dB between the highest and lowest coupling levels. As anexample, assume a simple diode detector is used which has about 25 dB ofdynamic range. The loop dynamic range will then be 25+[−9.5−(−46)]=61.6dB. The improvement over using no variable voltage divider can be morethan 36 dB. Equally important as enhancing a dynamic range is improvingthe output harmonics and IP3 of the AIMM module. The variable voltagedivider 550 can allow the detector input port 505 to be more isolated atthe higher power levels. This can improve linearity of the module forhigh signal levels.

Turning now to FIG. 6, generally at 600 are the functional blocks of avariable voltage divider 640, and the RF matching network 610 can becombined in hardware to some degree by understanding that the outputnode 625 of the matching network 610 can be connected to a shunt RFbranch comprised of a series string of capacitors 660 and to impedance635. An input node for RF_(in) 605 can also be connected to the RFmatching network 610. This string of series capacitors 660 can be a RFvoltage divider 640, and by selectively tapping into various circuitnodes along the string, one can obtain a variable output voltage divider640. In an embodiment of the present disclosure, this can be done with adigitally controlled RF switch 630. The switch 630 can be realized withFETs, MEMS, PIN diodes, or any other RF switch technology. Associatedwith variable voltage divider 640 is RF voltage detector 655 andcontroller 620, which is further connected to RF matching network 610via bias voltage driver circuit 615.

As a practical matter, the resistance of R1 645 can be much higher (>10times) than the reactance of the string of series capacitors 660 betweenthe tap point and ground. An alternative circuit to FIG. 6 would havethe resistor R₁ 645 moved to the capacitor side of the switch SW₁ 630and placed in each of the three lines going to the tap points. This willallow the resistors to be built on-chip with the tunable IC used in thematching network. Resister R4 can also be utilized at 650.

Some embodiments of the present disclosure can be implemented, forexample, using a machine-readable medium or article which can store aninstruction or a set of instructions that, if executed by a machine, forexample, by the system of FIG. 1 or FIG. 2, by controller 125 and 235 incommunication with bias voltage driver circuit 120 and 230, by processor355 of FIG. 3, or by other suitable machines, cause the machine toperform a method and/or operations in accordance with embodiments of thepresent disclosure. Such machine can include, for example, any suitableprocessing platform, computing platform, computing device, processingdevice, computing system, processing system, computer, processor, or thelike, and can be implemented using any suitable combination of hardwareand/or software.

The machine-readable medium or article can include, for example, anysuitable type of memory unit, memory device, memory article, memorymedium, storage device, storage article, storage medium and/or storageunit, for example, memory, removable or non-removable media, erasable ornon-erasable media, writeable or re-writeable media, digital or analogmedia, hard disk, floppy disk, Compact Disk Read Only Memory (CD-ROM),Compact Disk Recordable (CD-R), Compact Disk Re-Writeable (CD-RW),optical disk, magnetic media, various types of Digital Versatile Disks(DVDs), a tape, a cassette, or the like. The instructions can includeany suitable type of code, for example, source code, compiled code,interpreted code, executable code, static code, dynamic code, or thelike, and can be implemented using any suitable high-level, low-level,object-oriented, visual, compiled and/or interpreted programminglanguage, e.g., C, C++, Java, BASIC, Pascal, Fortran, Cobol, assemblylanguage, machine code, or the like.

An embodiment of the present disclosure can provide a machine-accessiblemedium that provides instructions, which when accessed, cause a machineto perform operations comprising adapting an RF matching network tomaximize RF power transferred from at least one RF input port to atleast one RF output port by controlling the variation of the voltage orcurrent to voltage or current controlled variable reactive elements insaid RF matching network to maximize the RF voltage at said at least oneRF output port. The machine-accessible medium of the present disclosurecan further comprise said instructions causing said machine to performoperations further comprising receiving information from a voltagedetector connected to said at least one RF output port which determinesthe voltage at said at least one RF output port and providing voltageinformation to a controller that controls a bias driving circuit whichprovides voltage or current bias to said RF matching network.

Some embodiments of the present disclosure can be implemented bysoftware, by hardware, or by any combination of software and/or hardwareas can be suitable for specific applications or in accordance withspecific design requirements. Embodiments of the present disclosure caninclude units and/or sub-units, which can be separate of each other orcombined together, in whole or in part, and can be implemented usingspecific, multi-purpose or general processors or controllers, or devicesas are known in the art. Some embodiments of the present disclosure caninclude buffers, registers, stacks, storage units and/or memory units,for temporary or long-term storage of data or in order to facilitate theoperation of a specific embodiment.

Throughout the aforementioned description, BST may be used as a tunabledielectric material that may be used in a tunable dielectric capacitorof the present disclosure. Paratek Microwave, Inc. (Paratek) hasdeveloped and continues to develop tunable dielectric materials that maybe utilized in embodiments of the present disclosure and thus thepresent disclosure is not limited to using BST material. This family oftunable dielectric materials may be referred to as Parascan™.

The term Parascan™ as used herein is a trademarked term indicating atunable dielectric material developed by Paratek. Parascan™ tunabledielectric materials have been described in several patents. Bariumstrontium titanate (BaTiO3-SrTiO3), also referred to as BSTO, is usedfor its high dielectric constant (200-6,000) and large change indielectric constant with applied voltage (25-75 percent with a field of2 Volts/micron). Tunable dielectric materials including barium strontiumtitanate are disclosed in U.S. Pat. No. 5,312,790 to Sengupta, et al.entitled “Ceramic Ferroelectric Material”; U.S. Pat. No. 5,427,988 bySengupta, et al. entitled “Ceramic Ferroelectric CompositeMaterial-BSTO—MgO”; U.S. Pat. No. 5,486,491 to Sengupta, et al. entitled“Ceramic Ferroelectric Composite Material-BSTO—ZrO2”; U.S. Pat. No.5,635,434 by Sengupta, et al. entitled “Ceramic Ferroelectric CompositeMaterial-BSTO-Magnesium Based Compound”; U.S. Pat. No. 5,830,591 bySengupta, et al. entitled “Multilayered Ferroelectric CompositeWaveguides”; U.S. Pat. No. 5,846,893 by Sengupta, et al. entitled “ThinFilm Ferroelectric Composites and Method of Making”; U.S. Pat. No.5,766,697 by Sengupta, et al. entitled “Method of Making Thin FilmComposites”; U.S. Pat. No. 5,693,429 by Sengupta, et al. entitled“Electronically Graded Multilayer Ferroelectric Composites”; U.S. Pat.No. 5,635,433 by Sengupta entitled “Ceramic Ferroelectric CompositeMaterial BSTO—ZnO”; U.S. Pat. No. 6,074,971 by Chiu et al. entitled“Ceramic Ferroelectric Composite Materials with Enhanced ElectronicProperties BSTO Mg Based Compound-Rare Earth Oxide”. These patents areincorporated herein by reference. The materials shown in these patents,especially BSTO—MgO composites, show low dielectric loss and hightunability. Tunability is defined as the fractional change in thedielectric constant with applied voltage.

Barium strontium titanate of the formula Ba_(x)Sr_(1-x)TiO₃ is apreferred electronically tunable dielectric material due to itsfavorable tuning characteristics, low Curie temperatures and lowmicrowave loss properties. In the formula Ba_(x)Sr_(1-x)TiO₃, x can beany value from 0 to 1, preferably from about 0.15 to about 0.6. Morepreferably, x is from 0.3 to 0.6.

Other electronically tunable dielectric materials may be used partiallyor entirely in place of barium strontium titanate. An example isBa_(x)Ca_(1-x)TiO₃, where x is in a range from about 0.2 to about 0.8,preferably from about 0.4 to about 0.6. Additional electronicallytunable ferroelectrics include Pb_(x)Zr_(1-x)TiO₃ (PZT) where x rangesfrom about 0.0 to about 1.0, Pb_(x)Zr_(1-x)SrTiO₃ where x ranges fromabout 0.05 to about 0.4, KTa_(x)Nb_(1-x)O₃ where x ranges from about 0.0to about 1.0, lead lanthanum zirconium titanate (PLZT), PbTiO₃,BaCaZrTiO.₃, NaNO₃, KNbO₃, LiNbO₃, LiTaO₃, PbNb₃O₆, PbTa₂O₆, KSr(NbO₃)and NaBa₂ (NbO₃)₅ KH₂PO₄, and mixtures and compositions thereof. Also,these materials can be combined with low loss dielectric materials, suchas magnesium oxide (MgO), aluminum oxide (Al₂O₃), and zirconium oxide(ZrO₂), and/or with additional doping elements, such as manganese (MN),iron (Fe), and tungsten (W), or with other alkali earth metal oxides(i.e. calcium oxide, etc.), transition metal oxides, silicates,niobates, tantalates, aluminates, zirconnates, and titanates to furtherreduce the dielectric loss.

In addition, the following U.S. patents and patent applications,assigned to the assignee of this application, disclose additionalexamples of tunable dielectric materials: U.S. Pat. No. 6,514,895,entitled “Electronically Tunable Ceramic Materials Including TunableDielectric and Metal Silicate Phases”; U.S. Pat. No. 6,774,077, entitled“Electronically Tunable, Low-Loss Ceramic Materials Including a TunableDielectric Phase and Multiple Metal Oxide Phases”; U.S. Pat. No.6,737,179 filed Jun. 15, 2001, entitled “Electronically TunableDielectric Composite Thick Films And Methods Of Making Same; U.S. Pat.No. 6,617,062 entitled “Strain-Relieved Tunable Dielectric Thin Films”;U.S. Pat. No. 6,905,989, filed May 31, 2002, entitled “TunableDielectric Compositions Including Low Loss Glass”; U.S. patentapplication Ser. No. 10/991,924, filed Nov. 18, 2004, entitled “TunableLow Loss Material Compositions and Methods of Manufacture and UseTherefore” These patents and patent applications are incorporated hereinby reference.

The tunable dielectric materials can also be combined with one or morenon-tunable dielectric materials. The non-tunable phase(s) may includeMgO, MgAl₂O₄, MgTiO₃, Mg₂SiO₄, CaSiO₃, MgSrZrTiO₆, CaTiO₃, Al.sub.2O₃,SiO₂ and/or other metal silicates such as BaSiO₃ and SrSiO₃. Thenon-tunable dielectric phases may be any combination of the above, e.g.,MgO combined with MgTiO₃, MgO combined with MgSrZrTiO₆, MgO combinedwith Mg₂SiO₄, MgO combined with Mg₂SiO₄, Mg₂SiO₄ combined with CaTiO₃and the like.

Additional minor additives in amounts of from about 0.1 to about 5weight percent can be added to the composites to additionally improvethe electronic properties of the films. These minor additives includeoxides such as zirconnates, tannates, rare earths, niobates andtantalates. For example, the minor additives may include CaZrO₃, BaZrO₃,SrZrO₃, BaSnO₃, CaSnO₃, MgSnO₃, Bi₃O₃/2SnO₂, Nd₂O₃, Pr₇O₁₁, Yb₂O₃,H_(o2)O₃, La₂O₃, MgNb₂O₆, SrNb₂O₆, BaNb₂O₆, MgTa₂O₆, BaTa₂O₆ and Ta₂O₃.

Films of tunable dielectric composites may comprise Ba1−xSrxTiO₃, wherex is from 0.3 to 0.7 in combination with at least one non-tunabledielectric phase selected from MgO, MgTiO₃, MgZrO₃, MgSrZrTiO₆, Mg₂SiO₄,CaSiO₃, MgAl₂O₄, CaTiO₃, Al₂O₃, SiO₂, BaSiO₃ and SrSiO₃. Thesecompositions can be BSTO and one of these components, or two or more ofthese components in quantities from 0.25 weight percent to 80 weightpercent with BSTO weight ratios of 99.75 weight percent to 20 weightpercent.

The electronically tunable materials may also include at least one metalsilicate phase. The metal silicates may include metals from Group 2A ofthe Periodic Table, i.e., Be, Mg, Ca, Sr, Ba and Ra, preferably Mg, Ca,Sr and Ba. Preferred metal silicates include Mg₂SiO₄, CaSiO₃, BaSiO₃ andSrSiO₃. In addition to Group 2A metals, the present metal silicates mayinclude metals from Group 1A, i.e., Li, Na, K, Rb, Cs and Fr, preferablyLi, Na and K. For example, such metal silicates may include sodiumsilicates such as Na₂SiO₃ and NaSiO₃-5H₂O, and lithium-containingsilicates such as LiAlSiO₄, Li2SiO₃ and Li₄SiO₃. Metals from Groups 3A,4A and some transition metals of the Periodic Table may also be suitableconstituents of the metal silicate phase. Additional metal silicates mayinclude Al₂Si₂O₇, ZrSiO₄, KalSi₃O₈, NaAlSi₃O₈, CaAl₂Si₂ O₈, CaMgSi₂O₆,BaTiSi₃O₉ and Zn₂SiO₄. The above tunable materials can be tuned at roomtemperature by controlling an electric field that is applied across thematerials.

In addition to the electronically tunable dielectric phase, theelectronically tunable materials can include at least two additionalmetal oxide phases. The additional metal oxides may include metals fromGroup 2A of the Periodic Table, i.e., Mg, Ca, Sr, Ba, Be and Ra,preferably Mg, Ca, Sr and Ba. The additional metal oxides may alsoinclude metals from Group 1A, i.e., Li, Na, K, Rb, Cs and Fr, preferablyLi, Na and K. Metals from other Groups of the Periodic Table may also besuitable constituents of the metal oxide phases. For example, refractorymetals such as Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta and W may be used.Furthermore, metals such as Al, Si, Sn, Pb and Bi may be used. Inaddition, the metal oxide phases may comprise rare earth metals such asSc, Y, La, Ce, Pr, Nd and the like.

The additional metal oxides may include, for example, zirconnates,silicates, titanates, aluminates, stannates, niobates, tantalates andrare earth oxides. Preferred additional metal oxides include Mg₂SiO₄,MgO, CaTiO₃, MgZrSrTiO₆, MgTiO₃, MgA₁₂O₄, WO3, SnTiO₄, ZrTiO₄, CaSiO₃,CaSnO₃, CaWO₄, CaZrO₃, MgTa₂O₆, MgZrO₃, MnO₂, PbO, Bi₂O₃ and La₂O₃.Particularly preferred additional metal oxides include Mg₂SiO₄, MgO,CaTiO₃, MgZrSrTiO₆, MgTiO₃, MgAl₂O₄, MgTa₂O₆ and MgZrO₃.

The additional metal oxide phases are typically present in total amountsof from about 1 to about 80 weight percent of the material, preferablyfrom about 3 to about 65 weight percent, and more preferably from about5 to about 60 weight percent. In one preferred embodiment, theadditional metal oxides comprise from about 10 to about 50 total weightpercent of the material. The individual amount of each additional metaloxide may be adjusted to provide the desired properties. Where twoadditional metal oxides are used, their weight ratios may vary, forexample, from about 1:100 to about 100:1, typically from about 1:10 toabout 10:1 or from about 1:5 to about 5:1. Although metal oxides intotal amounts of from 1 to 80 weight percent are typically used, smalleradditive amounts of from 0.01 to 1 weight percent may be used for someapplications.

The additional metal oxide phases can include at least two Mg-containingcompounds. In addition to the multiple Mg-containing compounds, thematerial may optionally include Mg-free compounds, for example, oxidesof metals selected from Si, Ca, Zr, Ti, Al and/or rare earths.

The illustrations of embodiments described herein are intended toprovide a general understanding of the structure of various embodiments,and they are not intended to serve as a complete description of all theelements and features of apparatus and systems that might make use ofthe structures described herein. Many other embodiments will be apparentto those of skill in the art upon reviewing the above description. Otherembodiments can be utilized and derived therefrom, such that structuraland logical substitutions and changes can be made without departing fromthe scope of this disclosure. Figures are also merely representationaland cannot be drawn to scale. Certain proportions thereof can beexaggerated, while others can be minimized. Accordingly, thespecification and drawings are to be regarded in an illustrative ratherthan a restrictive sense.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin a single embodiment for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

What is claimed is:
 1. A communication device, comprising: atransceiver; an antenna; and an RF matching network comprising aplurality of variable reactive elements, wherein the RF matching networkhas an RF input port coupled to the transceiver producing an RF signalsupplied to the RF input port, and wherein the RF matching networkcomprises an RF output port coupled to the antenna; a detector thatobtains a signal from the RF output port of the RF matching network anddetermines a signal parameter associated with the signal; and acontroller coupled with the detector and with the RF matching network,wherein the controller generates a plurality of bias signals forindependently controlling the plurality of variable reactive elementsbased on the signal parameter, wherein the RF matching network modifiessignal power transferred from the RF input port to the RF output portaccording to the plurality of bias signals applied to the plurality ofvariable reactive elements to vary a variable impedance of the RFmatching network.
 2. The communication device of claim 1, wherein theplurality of variable reactive elements includes a voltage tunabledielectric capacitor.
 3. The communication device of claim 1, whereinthe plurality of bias signals is generated by the controller based on amode of operation of the communication device.
 4. The communicationdevice of claim 3, wherein the mode of operation distinguishes between atransmit mode and a receive mode.
 5. The communication device of claim1, wherein the plurality of variable reactive elements includes areactive element configurable with a semiconductor device.
 6. Thecommunication device of claim 1, wherein the plurality of variablereactive elements includes a reactive element controlled with amicro-electro-mechanical systems (MEMS) device.
 7. The communicationdevice of claim 1, wherein the plurality of variable reactive elementsincludes a reactive element configurable with a mechanical switch. 8.The communication device of claim 1, wherein the plurality of biassignals includes digital signals.
 9. The communication device of claim1, wherein the controller generates the plurality of bias signals basedon an operating frequency of the communication device.
 10. Thecommunication device of claim 1, further comprising a charge pump thatincreases a voltage supply to each of the plurality of variable reactiveelements, wherein the voltage supply is based on the plurality of biassignals from the controller.
 11. The communication device of claim 10,wherein the voltage supply includes a negative voltage.
 12. Acommunication device, comprising: a transceiver; an antenna; and an RFmatching network comprising a plurality of variable reactive elements,wherein the RF matching network has an RF input port coupled to thetransceiver producing an RF signal supplied to the RF input port, andwherein the RF matching network comprises an RF output port coupled tothe antenna; a detector that obtains a signal from the RF output port ofthe RF matching network and determines a voltage magnitude associatedwith the signal; and a controller coupled with the detector and with theRF matching network, wherein the controller generates a plurality ofbias signals for independently controlling the plurality of variablereactive elements based on the voltage magnitude and based on a mode ofoperation of the communication device, wherein the RF matching networkmodifies signal power transferred from the RF input port to the RFoutput port according to the plurality of bias signals applied to theplurality of variable reactive elements to vary a variable impedance ofthe RF matching network.
 13. The communication device of claim 12,wherein the mode of operation distinguishes between a transmit mode anda receive mode.
 14. The communication device of claim 12, wherein theplurality of variable reactive elements includes a voltage tunabledielectric capacitor.
 15. The communication device of claim 12, whereinthe plurality of variable reactive elements includes a reactive elementconfigurable with a semiconductor device.
 16. The communication deviceof claim 12, wherein the plurality of variable reactive elementsincludes a reactive element controlled with a micro-electro-mechanicalsystems (MEMS) device.
 17. The communication device of claim 12, whereinthe plurality of variable reactive elements includes a reactive elementconfigurable with a mechanical switch.
 18. A communication device,comprising: a transceiver; an antenna; and an RF matching networkcomprising a plurality of voltage tunable dielectric capacitors, whereinthe RF matching network has an RF input port coupled to the transceiverproducing an RF signal supplied to the RF input port, and wherein the RFmatching network comprises an RF output port coupled to the antenna; adetector that obtains a signal from the RF output port of the RFmatching network and determines a signal parameter associated with thesignal; and a controller coupled with the detector and with the RFmatching network, wherein the controller generates a plurality of biassignals for independently controlling the plurality of voltage tunabledielectric capacitors based on the signal parameter and based on anoperating frequency of the communication device, wherein the RF matchingnetwork modifies signal power transferred from the RF input port to theRF output port according to the plurality of bias signals applied to theplurality of voltage tunable dielectric capacitors to vary a variableimpedance of the RF matching network.
 19. The communication device ofclaim 18, wherein the plurality of bias signals is generated by thecontroller based on a mode of operation of the communication device. 20.The communication device of claim 19, wherein the mode of operationdistinguishes between a transmit mode and a receive mode.